FWIW, these two datums aren't mutually exclusive.
If you have a high enough degree of certainty somebody could have a 99% chance of winning with an expected 50.1%/49.9% split. For the split to mean anything you need to know the confidence/variance.
If you have a high enough degree of certainty somebody could have a 99% chance of winning with an expected 50.1%/49.9% split. For the split to mean anything you need to know the confidence/variance.
I would guess they encountered it via a vaguely classical adjacent education or reading background, in that a (non geodesy / survey related) datum is a singular thing given, granted, assumed as fact, used in a reasoning chain.
More simply, the singular of data.
S'all Latin to me.